Basic mechanisms of the secretory process are studied in rat and human salivary gland cells. Techniques utilized include light and electron microscopy, enzyme-and immunocytochemistry, radioautography, and biochemistry. Major areas of investigations are: (1) localization of secretory and cellular proteins in developing and adult salivary glands using fluorescent and colloidal gold immunolabeling procedures; (2) structure and permeability properties of junctional complexes in rat salivary glands; and (3) the role of salivary duct cells in protein reabsorption.